A loop heat pipe system is used as a heat transport means for exhaust heat recovery, etc. For example, a loop heat pipe system is used in order to utilize automotive exhaust heat for engine warm-up, air conditioner, etc. The loop heat pipe system is also used for cooling an automotive inverter.
The loop heat pipe system is equipped with an evaporator and a condenser. For example, in the case of utilizing automotive exhaust heat for engine warm-up, in the evaporator, a liquid working fluid evaporates due to heat of exhaust gas, and vapor of the working fluid is obtained. Vapor of the working fluid is transported to the condenser, and in the condenser, heat is exchanged between the working fluid vapor and the engine cooling water, thereby rapidly raising the temperature of cooling water. Consequently, the engine warm-up time can be shortened and as a result, the fuel consumption rate can be improved. Furthermore, in the condenser, the working fluid is condensed from vapor into liquid due to heat exchange between the liquid working fluid and the engine cooling water, and the liquid working fluid is returned to the evaporator.
Patent Document 1 describes a multilayer wick used for an evaporator of a loop heat pipe system. The multilayer wick has a first layer and a second layer surrounding the first layer, in which the first layer is formed of a high thermally conductive material and the second layer is formed of a low thermally conductive material. Due to this configuration, heat for heating the multilayer wick is prevented from conducting to a liquid working fluid.
Patent Document 2 describes a loop heat pipe structure. The evaporator of the loop heat pipe structure has a first wick layer and a second wick layer disposed while covering the upper part of the first wick layer. The heat conductivity of the second wick layer is lower than the heat conductivity of the first wick layer, and heat is thereby prevented from escaping the first wick layer and heating a liquid working fluid.